Purification of hardwood oils



Patented Nov. 14, 1939 UNITED STATES PATENT OFFICE PURIFICATION OFHARDWOOD OILS No Drawing. Application March 1, 1938,

Serial No. 193,306

4 Claims.

This invention relates to the purification of oils derived from thedestructive distillation of hardwood, and particularly to thepurification of those oils known as neutral oils, such, for instance, as

5 the light acid oil and washed alcohol oil, described in my UnitedStates Patents 1,975,090 and 1,975,091. These oils are called neutraloils in contradistinction to caustic-soluble wood oils.

It is well known that these neutral oils contain, as impurities,phenolic derivatives and complex unsaturated compounds in varyingamounts. These impurities bring about darkening .of the wood oils whenthey are exposed to light and air, or stored in iron containers. Thedarkening is accelerated by heat.

The impurities also bring about corrosion of the iron containers. InUnited States Patent 2,095,857, of Carter and Fig'g, we have described amethod by which the amount of these impurities may be reduced to such anextent that the oils are no longer corrosive to ferrous containers, andthat their stability to light and to metals is improved. The Carter andFigg treatment consists in distilling the wood oils through a columnpacked with steel wool or other form of iron presenting a large surfacerelative to its mass. While the Carter and Figg method produces an oilwhich is non-corrosive to ferrous containers, the oil so purified is notentirely stable as to color when exposed to light and air, andparticularly when stored in ferrous containers and exposed to heat.

I have discovered that hardwood neutral oils can be purified, and theirstability to light, air, and metals greatly increased by extraction withethylene diamine, followed by removal of the residual ethylene diamine.If the residual ethylene diamine is not removed, thecolor will not bestable. I give below various illustrations of the way in which myinvention may be carried out.

Example 1.Neutral oil was distilled, the frac. tion distilling below 180C. at atmospheric pressure being taken. The usual acid content in thisfraction is 50-7 .0 grams per 100 cc., calculated as acetic acid. Theoil fraction was shaken thoroughly with 20% by volume of ethylenediamine. A vigorous reaction took place. The mixture was allowed tosettle, and the ethylene diamine layer was drawn off. The oil wasdistilled through steel wool, as described in patent 2,095,857. Thedistillate 'came over colorless up to the last 5-10%. A heavy, stifi,tarry residue was left in the base heater of the distilling apparatus.The distillation range of the vapors was 30-120 C. The distillate waswashed twice with two parts of water. The color of the washed distillatewas a a very, very light greenish yellow, which turned to a clear,reddish color after the oil had stood cold for a few days. It was muchmore stable as to color than a portion of the same oil fraction whichhad merely been distilled through steel wool.

Example 2.-Neutral oil was distilled, the fraction distilling below 180,C. at atmospheric pressure being taken. The oil fraction was'shakenthoroughly with 20% by volume of ethylene diamine. The mixture wasallowed to settle for one-half hour, and the ethylene diamine layer wasdrawn oil. The oil layer was washed twice with two parts of water, anddistilled through steel wool. The distillate was washed twice with twoparts otwater, shaken again with 20% by volume of ethylene diamine, andseparated immediately after settling. The oil layer was distilledthrough steel wool, and the distillate washed twice with two parts ofwater. The oil thus purified turned only slightly off color in 24 hoursof storage at C. in steel. Its saponiflcation number was 5.01, the lowsaponification number indicating a high degree of stability.

Example 3.-Neutral oil was distilled, the fraction distilling below 180C. being taken. The oil was washed twice with two parts of water. It wasthen agitated twice with two parts of a 2% solution of 50% caustic sodaat 50 C. for two hours, cooled, separated, and distilled through steelwool. The distillate was shaken thoroughly with 20% by volume ofethylene diamine, allowed to settle and the oil separated. The oil waswashed twice with two parts of water and separated. It was thendistilled through steel wool and again washed with two parts of water.The color of the purified oil was a clear light yellow. Itssaponification number was 3.06, indicating great stability. It turnedonly slightly off color in two days of storage at 75 C. in steel. Evenwhen stored in an open steel vessel and placed in the Fadeometer for 48hours it showed only very slight discoloration.

Example 4.Neutral oil is distilled under vacuum without fractionation,the entire distillate that comes over at 25" vacuum and lbs. steam beingcollected. 5% to 20% of ethylene diamine is added to the distillate, themixture is agitated thoroughly and allowed to settle, and the ethylenediamine layer is separated from the oil layer. The oil layer is washed,either with an equal part of water or with an equal part of a 1.0%solution by volume of sulfuric acid. The washed oil is vacuumdistilledthrough a column packed with steel wool, a rectifying column,dephlegmator and condenser, and the distillate that comes over at C. and25" vacuum is collected. Finally, the distillate is washed with an equalpart of a 1.0% solution by volume of sulfuric acid and then with anequal part of water. The ethylene diamine from the original ethylenediamine layer can be regenerated by washing with water or a weakalkaline solution, decanting, and separating the ethylene diamine fromwater by'fractional distillation.

It will be understood that purification by means of ethylene diamine canbe applied to light acid oil alone, washed alcohol oil alone, or to anyother neutral oil or combination of neutral oils derived from thedestructive distillation of hardwood. It will also be understood thatethylene diamine treatment, followed by removal of the residual ethylenediamine, may be used alone or in combination with other methods ofpurifying wood oils. It need not be used only in connection withdistillation through steel, wool, although I have discovered that thecombination of ethylene diamine treatment and distillation through steelwool gives a purer and more stable wood oil than any other treatment orcombination of treatments which I have investigated. It will beunderstood that iron in other forms presenting a large surface relativeto its weight may be used in place of steel wool. The wood oils purifiedby my novel process are useful as alcohol denaturants.

what I claim as my invention and desire to be secured by Letters Patentof the United States is:

1. A process of purifying and stabilizing "neutral oils derived from thedestructive'distillation of hardwood, comprising extraction ofimpurities therefrom with ethylene diamine and removal of the residualethylene diamine from the wood oil.

2. A process of purifying and stabilizing neutral" oils derived from thedestructive distillation of hardwood, comprising extracting impuritiestherefrom with ethylene diamine and washing out the residual ethylenediamine from the wood oil.

3. A process of purifying and stabilizing neutral"'oils derived from thedestructive distillation of hardwood, comprising extracting impuritiestherefrom with ethylene diamine, distilling the wood oil through iron ina form presenting a large surface relative to its mass, and washing outthe residual ethylene diamine from the'wood oil.

4. A process of purifying and stabilizing "neutralfoils derived'from thedestructive distillation of hardwood, comprising extracting impuritiestherefrom with ethylene diamine, distilling the wood oil through steelwool, and washing out the residual ethylene diamine from the wood oil.

LOUIS J. FIGG. JR.

